1. Field of the Invention
The present invention relates to a retardation plate and a fabrication method thereof, and also relates to a plate for circularly polarizing light, a xc2xd wave plate and a reflection-type liquid crystal display device utilizing said retardation plate. More specifically, the invention relates to a retardation plate and a fabrication method thereof, and a plate for circularly polarizing light, a xc2xd wave plate and a reflection-type liquid crystal display device utilizing said retardation plate which can be used in display devices of personal computers, AV devices, portable information communication devices, game and simulation devices, and a navigation system for cars and the like.
2. Description of the Related Art
A xc2xc wave plate whose retardation (Re) is xc2xc of a wavelength has a variety of uses. For example, it may be used in a reflection-type liquid crystal display device, in a pickup for an optical disk, in a glare proof film and the like. A xc2xd wave plate whose Re is xc2xd of the wavelength also has a variety of uses. These include use in a liquid crystal projector and the like. In order for the xc2xc wave plate and the xc2xd wave plate to be used for a variety of purposes, it is desired that the xc2xd wave plate and the xc2xc wave plate can sufficiently carry out their respective functions for incident light within the entire visible light region. Examples of a broad band retardation plate which can function sufficiently for incident light within the entire visible light region include those disclosed in Japanese Patent Application Laid-Open No. 5-27118, JP-A Nos. 5-100114, 10-68816, 10-90521, in which two sheets of polymer films having anisotropies different from each other are laminated.
However, in order to fabricate a conventional laminated type retardation plate, it is necessary to form two kinds of chips in which stretched double refraction films are cut in a direction having different angles from each other with respect to the direction of stretching, and to adhere these chips with an adhesive agent and laminate them. Further, adhering the two sheets of chips results not only in the increased costs of coating an adhesive material onto the chips, and chipping and adhering them, but also results in reduced performance due to angle shifts and the like when the chips are adhered. These effects on the performance cannot be ignored. Moreover, in a laminated type retardation plate formed by adhesion of the chips, there may be a problem of reduced performance due to increased thickness.
The present invention has been carried out in consideration of the foregoing problems, and an object of the present invention is to provide a reflection-type liquid crystal display device with improved display luminosity by utilizing a broad band retardation plate capable of being manufactured by a simple method and uniformly retarding incident light in the entire visible light region, specifically a broad band xcex/2 plate and a broad band plate for circularly polarizing light and the retardation plate. Moreover, another object of the present invention is to provide a method of fabricating a retardation plate in which a broad band retardation plate giving a uniform retardation to all of the incident lights can be fabricated by a simple process.
The present invention includes a retardation plate comprising a material including a positive intrinsic double refraction value and a material including a negative intrinsic double refraction value, with the materials resulting in retardation for wavelengths of electromagnetic radiation for the plate, and for wavelengths of 450 nm, 550 nm, and 650 nm, the plate retardation value for wavelengths of 450 nm is less than the plate retardation value for wavelengths of 550 nm, and the plate retardation value for wavelengths of 550 nm, is less than the plate retardation value for wavelengths of 650 nm.
The present invention also includes a retardation plate comprising a first layer which comprises a material including a positive intrinsic double refraction value and a second layer which comprises a material including a negative intrinsic double refraction value, wherein said first layer and said second layer each include lag axes, and are laminated to one another such that lag axes of said first layer and said second layer are substantially orthogonally crossed.
The present invention also includes a retardation plate, comprising a first layer which comprises a material including a positive intrinsic double refraction value and a second layer which comprises a material including a negative intrinsic double refraction value, wherein said first layer and said second layer each include molecular chains comprising an alignment direction substantially the same in both the first layer and the second layer.
The present invention also includes a xc2xd wave plate comprising a polarizing plate and a retardation plate laminated to the polarizing plate, the retardation plate comprising a material including a positive intrinsic double refraction value and a material including a negative intrinsic double refraction value, said retardation plate including retardation values for wavelengths of xcex, defined as Re(xcex), and for each of xcex=450 nm, xcex=550 nm and Re(xcex=450) less than Re(xcex=550) less than Re(xcex=650), 0.4xe2x89xa6Re(xcex)/xcexxe2x89xa60.6, the polarizing plate including a polarizing plate transmission axis and said retardation plate including a lag axis, with said lag and transmission axis crossing each other.
The present invention also includes a xc2xd wave plate comprising a polarizing plate and a retardation plate laminated to the polarizing plate, the retardation plate including a first layer comprising a material including a positive intrinsic double refraction value, and a second layer comprising a material including a negative intrinsic double refraction value, said first layer and said second layer comprising double refraction, each layer including a lag axis with the layers laminated to one another with the lag axis of one layer substantially orthogonal to the lag axis of the other layer, said retardation plate comprising retardation values for wavelengths of xcex, defined as Re(xcex), and for each of xcex=450 nm, 550 nm and 650 nm, 0.4xe2x89xa6Re(xcex)/xcexxe2x89xa60.6, and the polarizing plate including a polarizing plate transmission axis and said retardation plate including a lag axis with said lag axis and transmission axis crossing each other.
The present invention also includes a plate for circularly polarizing light, comprising a polarizing plate and a retardation plate laminated to the polarizing plate, the retardation plate comprising a material including a positive intrinsic double refraction value and a material including a negative intrinsic double refraction value, said retardation plate including retardation values for wavelengths of xcex, defined as Re(xcex), and for each of xcex=450 nm, xcex=550 nm and Re(xcex=450) less than Re(xcex=550) less than Re(xcex=650) 0.2xe2x89xa6Re(xcex)/xcexxe2x89xa60.3, and the polarizing plate including a polarizing plate transmission axis and said retardation plate including a lag axis, with said lag and transmission axis crossing each other.
The present invention also includes a plate for circularly polarizing light, comprising a polarizing plate and a retardation plate laminated to the polarizing plate, the retardation plate comprising a first layer comprising a material including a positive intrinsic double refraction value and a second layer comprising a material including a negative intrinsic double refraction value, said first layer and said second layer comprising double refraction, each layer including a lag axis with the layers laminated to one another with the lag axis of one layer substantially orthogonal to the lag axis of the other layer, said retardation plate comprising retardation value for wavelengths of xcex, defined as Re(xcex), and for each of xcex=450 nm, 550 nm and 650 nm, 0.2xe2x89xa6Re(xcex)/xcexxe2x89xa60.3, and the polarizing plate including a polarizing plate transmission axis and said retardation plate including a lag axis with said lag axis and the transmission axis crossing each other.
The present invention also includes a reflection-type liquid crystal display device comprising:
(a) a reflection plate;
(b) a polarizing plate; and
(c) a liquid crystal cell and a retardation plate disposed between the reflection and polarizing plates, the retardation plate comprising a material including positive intrinsic double refraction, and a material including negative intrinsic double refraction, wherein the materials result in retardation values for the retardation plate for at least wavelengths of 450 nm, 550 nm, and 650 nm, with the retardation value for wavelengths of 450 nm being less than the retardation value for wavelengths of 550 nm, and the retardation value for wavelengths of 550 nm, being less than the retardation value for wavelengths of 650 nm.
The present invention also includes a reflection-type liquid crystal display device comprising:
(a) a reflection plate;
(b) a polarizing plate;
(c) a liquid crystal cell and a retardation plate disposed between the reflection and polarizing plates, the retardation plate including:
(i) a first layer comprising a material including a positive intrinsic double refraction value and a lag axis; and
(ii) a second layer comprising a material including a negative intrinsic double refraction value and a lag axis, with the first and second layers laminated to one another with the lag axis of each layer substantially orthogonal to one another.
The present invention further includes a method of forming a retardation plate, the method comprising the steps of:
(a) extruding a first resin comprising a positive intrinsic double refraction value to form a first plate layer;
(b) extruding a second resin comprising a negative intrinsic double refraction value to form a second plate layer; and
(c) laminating the first and second plate layers to one another to form a laminate.